1. Field of the Invention
The present invention relates to a bonding apparatus and bonding method and more specifically to an apparatus and method that can accurately calculate the amount of offset between a processing member such as a bonding tool, etc. and a position detection imaging device that takes images of bonding objects.
2. Prior Art
In, for instance, a wire bonding apparatus, a position detection camera and a bonding arm are disposed on a bonding head that is carried on an XY table. The position detection camera images a reference pattern of a bonding member in order to specify the bonding points on bonding objects such as semiconductor devices, etc. The bonding arm has at its one end a tool (bonding tool) that performs bonding. The position detection camera and the tool are installed on the bonding head so that the optical axis of the position detection camera and the axial center of the tool are separated by a fixed distance. Thus, the tool and bonding arm do not interfere with the visual field of the position detection camera when the position detection camera images the reference pattern of the bonding member. The distance between the optical axis of the position detection camera and the axial center of the tool is generally referred to as the xe2x80x9coffsetxe2x80x9d.
Since the position detection camera determines a reference point that is used to ascertain the position to which the tool is moved, it is extremely important to ascertain exactly how far the position detection camera is offset from the tool. However, the actual offset amount varies from instant to instant according to the thermal expansion of the camera holder and bonding arm caused by radiant heat from the high-temperature bonding stage. Accordingly, the offset amount must be corrected at the time that bonding work is initiated and at an appropriate timing during the bonding work.
For this purpose, in a bonding method and apparatus (Japanese Patent No. 2982000) proposed by the present applicant, a reference member is disposed in a specified position, a position detection camera is moved to a point above the reference member of this reference member, and the positional relationship between the reference member and the optical axis of the position detection camera is measured. Then, a tool (bonding tool) is moved to a point above the reference member in accordance with an amount of offset that is stored in memory beforehand, and the positional relationship between the reference member and the tool is measured by an offset correction camera. The accurate offset amount is then determined by correcting the offset amount that is stored in memory beforehand based upon these measurement results. In this structure, the offset amount between the position detection camera and the tool is determined with good precision as a result of the interposition of the reference member.
However, the above structure has some problems. An offset correction camera that is used exclusively for offset correction must be installed separately from the position detection camera used to detect the positions of bonding points. As a result, the structure of the bonding apparatus becomes too complicated.
The present invention is to solve the above-described problem.
The object of the present invention is to provide an apparatus and method which operates without the use of an exclusive offset correction camera even in cases where a reference member is used.
In other word, the above object is accomplished by a unique structure of the present invention for a bonding apparatus, and the unique structure comprises: a position detection imaging device that images bonding objects, a reference member that is disposed in a specified position, and optical members that conduct image light of the reference member and a processing member, which processes (or perform bonding on) the bonding objects, to the position detection imaging device.
In the above structure, the optical members are provided so as to conduct image light of the processing member and reference member to the position detection imaging device. Thus, the position detection imaging device that detects the positions of the bonding objects images not only the processing member but also the reference member. Accordingly, the apparatus can operate without an exclusive offset correction camera even in cases where a reference member is used. In the following descriptions, the term xe2x80x9cprocessing memberxe2x80x9d refers to any of various types of working heads that perform physical work on semiconductor devices.
Furthermore, in the above structure, the optical members are provided so as to conduct the image light, which is of the processing member and the reference member and captured from a plurality of different directions, to the position detection imaging device.
As a result, images of the processing member and reference member are captured from a plurality of different directions. More accurate positional information can be thus obtained from these images.
Furthermore, in the above structure, the position detection imaging device can be equipped with a telecentric lens.
In cases where a position detection imaging device that detects the positions of bonding objects is used for the imaging of both the processing member and the reference member, the distance from the bonding objects to the position detection imaging device differs from the distance from the processing member and reference member to the position detection imaging device, so that the size of the images of the latter varies. Accordingly, it is conceivable that the positional relationship between the processing member and the reference member cannot be correctly detected. However, in the above structure, the position detection imaging device is equipped with a telecentric lens, and this telecentric lens possesses characteristics in which the image size (i.e., the distance from the optical axis) does not vary even if the position of the object of imaging fluctuates. Accordingly, the detection of positional relationships based on the imaging of the position detection imaging device can be accurately accomplished in all cases.
In addition, in the above structure, a corrective lens can be further disposed in the light path leading to the position detection imaging device, and images of the reference member and processing member are focused on the image-focusing plane of the position detection imaging device via the corrective lens.
In this structure, the corrective lens is further disposed in the light path leading to the position detection imaging device, and images of the reference member and processing member are focused on the image-focusing plane of the position detection imaging device via the corrective lens. Accordingly, the imaging (or taking of image) can be accomplished under good focusing conditions in all cases, even if the distance from the bonding objects to the position detection imaging device differs from the distance from the processing member and reference member to the position detection imaging device.
Furthermore, in the present invention, the corrective lens can be held as an integral unit with the reference member.
In this structure, the corrective lens is integral with the reference member. Accordingly, when the position detection imaging device and processing member are moved in order to image the processing member and reference member, the corrective lens is brought to be in the light path that leads to the position detection imaging device. In other words, the corrective lens is interposed in and removed from the light path by an extremely simple structure.
The above object is accomplished by a further unique structure of the present invention for a bonding apparatus that comprises: a position detection imaging device that takes images of bonding objects; a reference member that is disposed in a specified position; a light source that illuminates a processing member, which processes the bonding objects, and the reference member; and a screen member onto which images of the processing member and the reference member are projected by the illumination from the light source, and in this structure, the distance from the position detection imaging device to the bonding objects when the position detection imaging device is in an attitude in which the bonding objects are imaged by the position detection image device is substantially equal to the distance from the position detection imaging device to the screen member when the position detection imaging device is in an attitude in which the processing member is caused to approach the reference member.
In the above structure, images of the processing member and reference member illuminated by the light source are projected onto a screen member. The distance from the position detection imaging device to the bonding objects when the position detection imaging device is in the attitude in which the position of the bonding objects is detected by the position detection imaging device is set so that this distance is substantially equal to the distance from the position detection imaging device to the screen member when the position detection imaging device is in an attitude in which the processing member is caused to approach the reference member. Accordingly, the screen member can be imaged under focused conditions similar to those obtained when the bonding objects are imaged by the position detection imaging device. As a result, such imaging can be accomplished under good focusing conditions in all cases.
The above object is further accomplished by unique steps of the present invention employed in a bonding apparatus that includes a position detection imaging device that images bonding objects, a processing member which is installed so as to be offset with respect to the position detection imaging device and to process the bonding objects, and a reference member that is disposed in a specified position, and the unique steps of the present invention comprises:
a step in which the positional relationship between the reference member and the position detection imaging device in a first attitude in which the position detection imaging device is caused to approach the reference member is measured by the position detection imaging device,
a step in which image light of the reference member and the processing member in a second attitude in which the processing member is caused to approach the reference member is conducted to the position detection imaging device, and the positional relationship between the processing member and the reference member is measured by the position detection imaging device, and
a step in which the accurate offset amount is determined based upon the above measurement results and the movement amounts of the position detection imaging device and the processing member between the first attitude and second attitude.
Furthermore, the above object is accomplished by a unique structure for a bonding apparatus that comprises:
a position detection imaging device that images bonding objects,
a processing member which is installed so as to be offset with respect to the position detection imaging device and to process the bonding objects,
a reference member that is disposed in a specified position, and
an operation control device that determines the amount of offset based upon:
the measured value obtained when the positional relationship between the reference member and the position detection imaging device in a first attitude in which the position detection imaging device is caused to approach the reference member is measured by the position detection imaging device,
the measured value obtained when image light of the reference member and the processing member in a second attitude in which the processing member is caused to approach the reference member is conducted to the position detection imaging device, and the positional relationship between the processing member and the reference member is measured by the position detection imaging device, and
the above measurement results and the movement amounts of the position detection imaging device and the processing member between the above first and second attitudes.